Adhesives with low VOC and fogging values

ABSTRACT

The invention relates to hotmelt adhesives based on polyesters, having low VOC and fogging values. In particular, the invention relates to reactive hotmelt adhesives including polyesters containing at least 50 mole percent, based on the polycarboxylic acid components, of terephthalic acid or a derivative thereof and containing at least 40 mole percent, based on the polyol components, of diols of the formula HO—(CH 2 ) x —OH with x≥6.

This application is a national stage application under 35 U.S.C. § 371of International Application No. PCT/EP2016/054089 filed 26 Feb. 2016,which claims priority to EP Application No. 15157142.9 filed 2 Mar.2015, the disclosures of which are expressly incorporated herein byreference.

FIELD

The invention relates to adhesives based on polyester polyols, havinglow VOC and fogging values.

BACKGROUND

Hotmelt adhesives are an important adhesive class for many applications,for example in the automotive sector, in the packaging sector, infurniture production or in textile bonding. They are solid at roomtemperature and are melted by heating, and are applied to the substratein substance at elevated temperature. In the course of cooling, theysolidify again and thus ensure a firm adhesive bond after only a shorttime.

A subgroup of the hotmelt adhesives is that of reactive hotmeltadhesives which, after application, additionally crosslink and thus cureirreversibly to form a thermoset. As compared with the non-crosslinking,purely physically curing thermoplastic hotmelt adhesives, the additionalchemical curing leads to a higher stability of the adhesive bond.Reactive hotmelt adhesives are particularly suitable for bonds in theautomotive and transport sector and the packaging sector, and in theconstruction industry, textile industry and the wood-processingindustry.

A preferred example of reactive hotmelt adhesives is one-packmoisture-curing hotmelt adhesives. These are generallyisocyanate-functionalized polymers obtainable by reacting polyols orpolyol mixtures with an excess of polyisocyanates.

The polyols may be any desired polymer bearing hydroxyl groups. Examplesof these include polycarbonate diols, hydroxyl-terminatedpolybutadienes, polyethers or polyhydroxyacrylates orpolyhydroxymethacrylates. Particular preference is given to polyesterpolyols. These can be prepared, for example, via the ring-openingpolymerization of lactones and preferably via the solvent-free meltcondensation of polyols with polycarboxylic acids or derivativesthereof. Preference is given to linear bifunctional polyester polyolsformed from diols and dicarboxylic acids, diesters and/or dianhydrides.Reactive hotmelt adhesives based on polyester polyols exhibit goodadhesion to a multitude of substrates, since the ester groups can bindto the substrate surface via hydrogen bonds. In addition, it is possibleto adjust the polymer properties and hence also the adhesive propertiesover a wide range via the nature and ratio of the comonomers.

In the production of the aforementioned systems, it should be ensuredthat the polymers obtained have minimum VOC values. VOC or VOCs(volatile organic compound(s)) is the collective term for organic, i.e.carbon-containing, substances which evaporate readily and are thereforevolatile.

A disadvantage is that several side reactions can occur in the course ofmelt condensation of diols with dicarboxylic acids, diesters and/ordianhydrides. One of these is the formation of cyclic dimers by ringclosure of a diol molecule with a dicarboxylic acid derivative. Thecyclic dimers form via an equilibrium reaction from linear dimers, whichform in turn by transesterification reactions at the chain ends of thelinear polyester chains (cf. EP 1571171). This means that a proportionof cyclic dimers is always present as well as the linear polyester.Depending on the size and stability of the ring, the typical proportionis up to 1% by weight (cf. U.S. Pat. No. 5,712,320).

The volatility of the cycles depends on the ring size and hence dependson the nature of the monomer units used. For example, adipic acid anddiethylene glycol form a cyclic diethylene glycol adipate composed of atotal of 13 ring atoms which sublimes readily (cf. U.S. Pat. No.5,712,320). Since the cyclic dimers do not have any hydroxylfunctionality, they do not react with isocyanate groups and are notincorporated into the polyurethane network. The cycles can thereforeevaporate off or migrate out of the cured adhesive. This is problematicparticularly in the case of bonds in motor vehicle interiors and in thefood packaging sector. In the case of food packaging, the volatileconstituents can migrate into the food and alter the taste or damage thefood in such a way as to constitute a health concern. In the automotivesector, the volatile constituents accumulate in the breathable airwithin the passenger cell and can cause an unpleasant odor. These may beof concern to health. It is particularly critical when the outgassingsubstances are deposited on cold surfaces such as the windscreen andlead to visual impairment. This effect is generally referred to as“fogging”.

For the reasons mentioned above, for applications in the automotiveinterior sector, there is a demand for components and adhesives,sealants and coatings materials having low VOC and fogging values, whichare generally measured by the industrial standard VDA 278. The standarddefines the test conditions for determination of the emission values atparticular temperatures. According to the limits required for curedadhesives and sealants of defined layer thickness, the VOC value, whichis the proportion of volatile organic substances emitted as gases at 90°C. within 30 minutes, must not exceed 100 μg/g. In addition, what iscalled the FOG value, which is a measure of the amount of organicemissions at 120° C. within 30 minutes after prior measurement of theVOC value, must not be higher than 250 μg/g.

The literature, for example patent applications DE 19528539 and DE19601410, JP 2004107457 and EP 1481998, describes various attempts toremove volatile cycles by distillation at elevated temperatures andunder reduced pressure. If, for example, a polyester melt, after thecondensation, is cooled down rapidly to temperatures below the softeningpoint, it is possible to reduce the proportion of cyclic components.However, as soon as the polyester is melted again, the concentration ofdimeric cycles rises again, since the cyclic components reform as aresult of the equilibrium reaction.

Cured polyurethane hotmelt adhesives based on amorphous solid or liquidpolyester polyol mixtures in particular combinations satisfy the limitsof the automotive industry according to VDA 278. In contrast, curedformulations which, in addition to amorphous polyester polyols, comprisesolid, crystalline or semicrystalline polyester polyols that arecustomary on the market have excessively high VOC and FOG values and donot satisfy the limits according to VDA 278. The reason is that themonomer units used customarily for the synthesis of crystallinepolyesters form dimeric cycles which are volatile in the range relevantfor VDA 278. These include, in particular, the dimers formed fromaliphatic diols and dicarboxylic acids, for example cyclic neopentylglycol adipate, butanediol adipate, hexanediol adipate, hexanediolsebacate, etc.

U.S. Pat. No. 5,712,230, for example, claims low-emission polyesterpolyurethane foams in which polyesters wherein the monomers cannot formany cycles having ring sizes between 12 and 14 atoms are used.

WO 2012125353 claims polyester polyols based on phthalic anhydride andselected diol units, for example ethylene glycol, propylene glycol,neopentyl glycol or hexanediol. The polyester polyols do have a lowconcentration of cyclic dimers, but the polymers are not crystalline.

SUMMARY

The problem addressed by the present invention was therefore that ofproviding adhesive or sealant formulations based on reactive hotmeltadhesives, which satisfy the same demands as the prior art formulationsand have low VOC and FOG values and meet the limits of the automotiveindustry according to standard VDA 278. Furthermore, the hotmeltadhesive formulation should also have a low cycle concentration on apermanent basis, i.e. even after storage of the systems used, forexample in the melt. After curing, for example with diisocyanates, it isgenerally no longer possible for any dimeric cycles to form.

The aforementioned complex profile of requirements is achieved throughuse of specific polyesters according to the present invention inreactive hotmelt adhesives.

DETAILED DESCRIPTION

The present invention accordingly first provides for the use ofpolyesters containing at least 50 mole percent, based on thepolycarboxylic acid components, terephthalic acid or a derivativethereof and containing at least 40 mole percent, based on the polyolcomponents, of diols of the formula HO—(CH₂)_(x)—OH with x≥6 in reactivehotmelt adhesives, preferably in hotmelt adhesives based onpolyurethanes.

It has been found that, surprisingly, the monomer combinations of theinvention give solid, crystalline or semicrystalline polyester polyolshaving a melting point above room temperature, which have low VOC andFOG values in the reactive hotmelt adhesive after curing.

The emission values measured according to VDA 278, even in the case offormulations containing exclusively the crystalline or semicrystallinepolyesters according to the invention as polyols, are at lower measuredvalues than conventional polyester polyols, for example hexanedioladipate. According to the invention, the VOC and FOG values are withinthe limits of VDA 278.

The polyesters used in accordance with the invention feature theobligatory proportion of terephthalic acid or a derivative thereof anddiols of the formula HO—(CH₂)_(x)—OH with x≥6.

The polyesters used in accordance with the invention contain at least 50mole percent, based on the polycarboxylic acid components, ofterephthalic acid or a derivative thereof. Suitable derivatives areespecially esters of terephthalic acid. The proportion of terephthalicacid or derivatives thereof, based on the total proportion ofpolycarboxylic acids, is at least 50 mole percent, preferably at least60 mole percent.

In addition, the polyester used in accordance with the invention maycontain further di- or polycarboxylic acids. The remaining di- orpolycarboxylic acids or derivatives thereof may be as desired. Examplesof suitable di- and/or polycarboxylic acids and derivatives thereof arefirstly further aromatic compounds such as isophthalic acid,naphthalenedicarboxylic acid and phthalic anhydride. Further examplesare cyclic and linear aliphatic dicarboxylic acids such ascyclohexanedicarboxylic acid, hexahydrophthalic acid, succinic acid,glutaric acid, adipic acid, sebacic acid, azelaic acid,dodecane-1,12-dicarboxylic acid, brassylic acid and the diesters andanhydrides thereof. It is also possible to use polycarboxylic acidshaving more than two functional groups, for example trimelliticanhydride.

In the context of the present invention, di- or polycarboxylic acids arealso understood to mean derivatives thereof, for example esters oranhydrides.

Suitable diols of the formula HOOC—(CH₂)_(x)—COOH with x≥6 areespecially hexanediol, nonanediol, decanediol and dodecanediol,particular preference being given to using hexanediol.

The proportion of these diols, based on the total proportion of polyols,is at least 40 mole percent, preferably at least 50 mole percent andvery preferably 100 mole percent.

In addition, the polyester used in accordance with the invention maycontain further di- or polyols. Examples of suitable di- or polyols andderivatives thereof are aliphatic diols, for example monoethyleneglycol, diethylene glycol, propane-1,3-diol, propane-1,2-diol,butane-1,4-diol, pentane-1,5-diol, methylpropanediol, dicidol,cyclohexanedimethanol, butylethylpentanediol, neopentyl glycol. It isalso possible to use polyols having more than two functional groups, forexample trimethylolpropane, pentaerythritol or glycerol. Moreover,lactones and hydroxycarboxylic acids may be used as diols or polyols.

The polyesters described allow the provision of hotmelt adhesives havinglow VOC and FOG values, since cyclic dimers formed from these monomersare comparatively stiff owing to the aromatic ring structure; therefore,the equilibrium is probably strongly to the side of the linear ratherthan the cyclic dimers.

The polyesters are preferably synthesized via a melt condensation. Forthis purpose, the aforementioned di- or polycarboxylic acids and di- orpolyols are initially charged and melted in an equivalents ratio ofhydroxyl to carboxyl groups of 0.5 to 1.5, preferably 1.0 to 1.3. Thepolycondensation is effected in the melt at temperatures between 150 and280° C. within 3 to 30 hours. First of all, a major part of the amountof water released is distilled off under atmospheric pressure. In thefurther course, the remaining water of reaction, and also volatilediols, are eliminated, until the target molecular weight is achieved.Optionally this may be made easier through reduced pressure, through anenlargement in the surface area, or by the passing of an inert gasstream through the reaction mixture. The reaction may additionally beaccelerated by addition of an azeotrope former and/or of a catalystbefore or during the reaction. Examples of suitable azeotrope formersare toluene and xylenes. Typical catalysts are organotitanium ororganotin compounds such as tetrabutyl titanate or dibutyltin oxide.Also conceivable are catalysts based on other metals, such as zinc orantimony, for example, and also metal-free esterification catalysts.Also possible are further additives and process aids such asantioxidants or color stabilizers.

The polyesters used in accordance with the invention have at least onehydroxyl and/or carboxyl end group, the functionality preferably beingbetween 2.0 and 3.0.

The concentration of hydroxyl end groups, determined by titrimetricmeans to DIN 53240-2, is between 0 and 200 mg KOH/g, preferably between5 and 50 mg KOH/g.

The concentration of acid end groups, determined to DIN EN ISO 2114, isbetween 0 and 50 mg KOH/g, but preferably below 2 mg KOH/g.

The number-average molecular weight of the polyesters used in accordancewith the invention is 500-30 000 g/mol, preferably 1000-20 000 g/mol. Itis determined to DIN 55672-1 by means of gel permeation chromatographyin tetrahydrofuran as eluent and polystyrene for calibration.

The polyesters of the invention have one or more melting points.Preferably, at least one melting point is above room temperature, 23° C.The sum of the individual enthalpies of fusion in the first heatingcurve is 1-300 J/g, preferably 5-130 J/g.

In addition, the polyester of the invention may have a glass transitiontemperature in the range from −80° C. to 100° C., preferably between−60° C. and 0° C.

The thermal properties are determined by the DSC method to DIN 53765.For the determination of the melting points the first heating curve isconsulted, and for the determination of the glass transition temperaturethe second heating curve.

In the reactive hotmelt adhesives of the invention, preference is givento using mixtures of different polyester polyols, since it is possibleby means of a controlled mixture to establish a balanced profile ofproperties matched to the application. More particularly, amorphous,non-crystalline polyester polyols that are solid or liquid at roomtemperature are combined with solid, crystalline polyester polyols. Theuse of crystalline components can achieve, inter alia, rapid physicalsetting and hence high initial strength. High initial strengths allowrapid further processing of the bonded component and hence short cycletimes. Therefore, a certain proportion of crystalline polyester polyolsin the hotmelt adhesive formulation is required.

According to the present invention, the hotmelt adhesives are reactivehotmelt adhesives (reactive hotmelts, RHM), which additionally crosslinkchemically, preference being given especially to moisture-curing hotmeltadhesives.

When employed in reactive hotmelt adhesives, the number-averagemolecular weight of the polyesters used in accordance with the inventionis preferably 500-10 000 g/mol, more preferably 2000-8000 g/mol.

The proportion of the polyester used in accordance with the invention inthe formulation is, based on the overall formulation, 1-99 percent byweight, preferably 5-85 percent by weight and more preferably 10-70percent by weight.

This assures a sufficient setting speed and, as a result of this, asufficient handling strength of the reactive hotmelt immediately afterthe adhesive application.

In preferred embodiments, other polyols are also present in the reactivehotmelt adhesives as well as the polyesters used in accordance with theinvention, and these should be understood to mean, for example,polyester polyols, polyether polyols and any other hydroxyl-functionalcomponents. These polyols may be chosen as desired in principle.However, the polyols used should not significantly increase the VOC andFOG values of the formulation. Preferably, the VOC and FOG values of theindividual polyols, based on the proportion thereof in the overallformulation, should not exceed the required limits according to VDA 278.

The polyester polyols added may be liquid or solid, amorphous or(semi)crystalline polyesters having molecular weights having a numberaverage between 500 g/mol and 30 000 g/mol, preferably between 2000g/mol and 10 000 g/mol (calculated from the hydroxyl number), preferencebeing given to using linear polyester polyols. The polyether polyolsadded are polyether di- and triols. Examples of these are homo- andcopolymers of ethylene glycol, propylene glycol and butane-1,4-diol. Themolecular weight (number average) of the polyether polyols added shouldbe within a range from 200 g/mol to 10 000 g/mol, preferably between 400g/mol and 6000 g/mol. Examples of freely selectable hydroxyl-functionalcomponents are functionalized (H-acidic) thermoplastic polyurethanes(TPUs) or polyacrylates and/or ethylene-vinyl acetate copolymers (EVA).

The moisture-crosslinking hotmelt adhesives are obtained by the reactionof the polyol mixture with polyisocyanates. In the adhesives, the OH:NCOratio of polyester to isocyanate is generally 1:1.2 to 1:3, preferably1:1.5 to 1:2.5.

The polyisocyanates may be di- and/or multifunctional, aromatic,aliphatic and/or cycloaliphatic isocyanates, and carbodiimide-modifiedisocyanates or isocyanate-terminated prepolymers. Aromaticpolyisocyanates are particularly preferred. Examples of polyisocyanatesare diphenylmethane 4,4′-diisocyanate, diphenylmethane2,4′-diisocyanate, toluene diisocyanate isomers, isophoronediisocyanate, hexamethylene diisocyanate, dicyclohexylmethane4,4′-diisocyanate and mixtures thereof. They are especiallydiphenylmethane 4,4′-diisocyanate and mixtures of diphenylmethane4,4′-diisocyanate and diphenylmethane 2,4′-diisocyanate.

Apart from the polyesters and polyisocyanates used in accordance withthe invention, the adhesive formulation may contain up to 50% by weight,based on the overall formulation, of further additives which ensureimproved hydrolysis stability, for example. Here too, it should beensured that the VOC and fogging values of the overall formulation arenot increased significantly.

These additions may be: nonfunctionalized polymers, for examplethermoplastic polyurethanes (TPUs) and/or polyacrylates and/orethylene-vinyl acetate copolymers (EVA); pigments or fillers, forexample talc, silicon dioxide, titanium dioxide, barium sulphate,calcium carbonate, carbon black or color pigments, tackifiers, forexample rosins, hydrocarbon resins, phenol resins, and ageingstabilizers and auxiliaries.

In a preferred embodiment, the moisture-crosslinking hotmelt adhesivesadditionally contain organosilanes, as well as or in place of thepolyisocyanates. The polyesters used in accordance with the inventioncan be functionalized by a stepwise reaction with polyisocyanates togive isocyanate-terminated prepolymers and subsequent reaction withorganosilanes, or by reaction with an adduct formed from polyisocyanatesand organosilanes.

In the simplest case, the polyesters are reacted with anisocyanatoalkylsilane in an OH/NCO ratio of 1:1 to 1:1.5.

Examples of organosilanes are aminopropyltrimethoxysilane,aminopropyltriethoxysilane, N-methylaminopropyltrimethoxysilane,N-cyclohexylaminopropyltrimethoxysilane,N-phenylaminopropyltrimethoxysilane, mercaptopropyltrimethoxysilane,mercaptotriethoxysilane.

In the simplest case, the reactive hotmelt adhesive of the invention isproduced by mixing the individual components in a stirred vessel with orwithout solvent, preferably in the melt. The melting temperature isguided by the viscosity of the constituents. It is typically within arange from 100 to 180° C.

The above-described reactive, especially moisture-curing, hotmeltadhesives, depending on the viscosity of the respective formulation, canbe applied at temperatures between 50 and 200° C., preferably between 80and 150° C.

The present invention likewise provides reactive hotmelt adhesivescomprising polyesters containing at least 50 mole percent, based on thepolycarboxylic acid components, terephthalic acid or a derivativethereof and containing at least 40 mole percent, based on the polyolcomponents, of diols of the formula HO—(CH₂)_(x)—OH with x≥6.

The reactive hotmelt adhesives of the invention are particularlysuitable for production of adhesive bonds of a variety of substrates,especially for bonding of metallic substrates and textiles, and veryparticularly for bonding of various plastics. The nature and extent ofthe bonding are unlimited. Preferably, the bonds are bonds in the woodand furniture industry (for example assembly bonding and the laminationof decorative films onto fiberboard), in the automotive sector (forexample laminations of films or textiles onto door side parts, innerroof linings, seat manufacture and retainer bonds), in the constructionindustry, shoe industry and textile industry, and in window construction(for example for profile ensheathing). In addition, the adhesives of theinvention are suitable in the packaging industry, as sealants and ascoating material.

The reactive hotmelt adhesives of the invention are suitable for useeither in one-pack or in two-pack systems.

In the case of the one-pack adhesives, the mixture is produced at adifferent time from the adhesive application, more particularly at amuch earlier time. The application of the polyurethane adhesive of theinvention is followed by curing, for example by moisture-induced orthermally induced reaction of the co-reactants present in the adhesive.

In the case of the two-pack adhesives, the mixture is produced directlyprior to adhesive application. The drawback of two-pack application ascompared with one-pack application is the increased level of technicalcomplexity and greater proneness to error, for example in the mixingoperation.

Even in the absence of further information it is assumed that a personskilled in the art can make very extensive use of the above description.The preferred embodiments and examples are therefore to be interpretedmerely as descriptive disclosure, and certainly not as disclosure thatis in any way limiting.

The present invention is explained in more detail below with referenceto examples. Alternative embodiments of the present invention areobtainable analogously.

EXAMPLES Example 1: Polyester 1 (Inventive)

5.47 kg of dimethyl terephthalate (31.9 mol) are melted together with3.77 kg of hexane-1,6-diol (31.9 mol), 1.58 kg of butane-1,4-diol (17.6mol) and 1 g (0.01 percent by weight) of a titanium catalyst in a flaskwith a distillation attachment under nitrogen. At a temperature of 210°C., the majority of the methanol formed is distilled off within abouttwo to four hours. Thereafter, 1.34 kg of isophthalic acid (8.1 mol) and0.59 kg of adipic acid (4.0 mol) are charged, the temperature isincreased to 230° C., and the majority of the water of reaction formedis distilled off within about four to six hours. Subsequently, thepressure in the apparatus is lowered stepwise down to 10 mbar. Thereaction has ended when no acid end groups are present any longer (acidnumber<1 mg KOH/g) and a concentration of hydroxyl end groups of 30 mgKOH/g has been attained. The polyester has a melting point of 89° C.with an enthalpy of fusion of 30 J/g. After reaction withdiphenylmethane diisocyanate, used in an NCO:OH ratio of 2.2, and curingin a climate-controlled cabinet, the polyester has a VOC value of 10mg/kg and a fogging value of 138 mg/kg, measured in accordance with VDA278.

Example 2: Polyester 2 (Inventive)

961 g of dimethyl terephthalate (5.0 mol) are melted together with 524 gof hexane-1,6-diol (4.4 mol), 220 g of butane-1,4-diol (2.4 mol) and 0.3g (0.02 percent by weight) of a titanium catalyst in a flask with adistillation attachment under nitrogen. At a temperature of 210° C., themajority of the methanol formed is distilled off within about two tofour hours. Thereafter, 206 g of isophthalic acid (1.2 mol) are charged,the temperature is increased to 230° C., and the majority of the waterof reaction formed is distilled off within about four to six hours.Subsequently, the pressure in the apparatus is lowered stepwise down to10 mbar. The reaction has ended when no acid end groups are present anylonger (acid number<1 mg KOH/g) and a concentration of hydroxyl endgroups of 30 mg KOH/g has been attained. The polyester has a meltingpoint of 98° C. with an enthalpy of fusion of 37 J/g. After reactionwith diphenylmethane diisocyanate, used in an NCO:OH ratio of 2.2, andcuring in a climate-controlled cabinet, the polyester has a VOC value of3 mg/kg and a fogging value of 15 mg/kg, measured in accordance with VDA278.

Example 3: Polyester V1 (Non-inventive)

2.48 kg of dimethyl terephthalate (12.8 mol) are melted together with5.09 kg of butane-1,4-diol (56.7 mol) and 1 g (0.01 percent by weight)of a titanium catalyst in a flask with a distillation attachment undernitrogen. At a temperature of 210° C., the majority of the methanolformed is distilled off within about two to four hours. Thereafter, 2.86kg of isophthalic acid (17.2 mol) and 2.19 kg of adipic acid (15.0 mol)are charged, the temperature is increased to 230° C., and the majorityof the water of reaction formed is distilled off within about four tosix hours.

Subsequently, the pressure in the apparatus is lowered stepwise down to10 mbar. The reaction has ended when no acid end groups are present anylonger (acid number<1 mg KOH/g) and a concentration of hydroxyl endgroups of 30 mg KOH/g has been attained. The polyester has a meltingpoint of 92° C. with an enthalpy of fusion of 6 J/g. After reaction withdiphenylmethane diisocyanate, used in an NCO:OH ratio of 2.2, and curingin a climate-controlled cabinet, the polyester has a VOC value of 186mg/kg and a fogging value of 10 mg/kg, measured in accordance with VDA278.

The invention claimed is:
 1. A reactive hotmelt adhesive comprising a polyester containing at least 50 mole per cent, based on the polycarboxylic acid components, of terephthalic acid or a derivative thereof and containing at least 40 mole per cent, based on the polyol components, of diols of the formula HO—(CH₂)_(x)—OH with x ≥6, wherein the number-average molecular weight of the polyester is from 500 to 30,000 g/mol; wherein the polyester has a melting point of greater than 23° C., a sum of individual enthalpies of fusion in the first heating curve of 5 to 130 J/g, and a glass transition temperature of from −80° C. to 0° C.
 2. The reactive hotmelt adhesive according to claim 1, wherein hexanediol, nonanediol, decanediol and dodecanediol are used as diols of the formula HO—(CH₂)_(x)—OH, and wherein the number-average molecular weight of the polyester is from 1,000 to 20,000 g/mol.
 3. The reactive hotmelt adhesive according to claim 1, wherein the reactive hotmelt adhesive has a VOC value which does not exceed 100 μg/g and a FOG value which is not higher than 250 μg/g.
 4. An adhesive bond comprising the reactive hotmelt adhesive according to claim 3, wherein the number-average molecular weight of the polyester is from 1,000 to 20,000 g/mol, and wherein the reactive hotmelt adhesive has a VOC value from 3 μg/g to 10 μg/g and a FOG value of from 15 to 138 μg/g.
 5. A wood product comprising the adhesive bond according to claim
 4. 6. A sealant comprising the reactive hotmelt adhesive according to claim
 3. 7. The adhesive bond according to claim 4, wherein the reactive hotmelt adhesive are used in one-pack or two-pack systems.
 8. A coating material comprising the reactive hotmelt adhesive according to claim
 3. 9. A furniture product comprising the reactive hotmelt adhesive according to claim
 3. 10. An automobile or automobile component comprising the reactive hotmelt adhesive according to claim
 3. 11. A shoe or shoe component comprising the reactive hotmelt adhesive according to claim
 3. 12. A textile or textile component comprising the reactive hotmelt adhesive according to claim
 3. 13. A window or window component comprising the reactive hotmelt adhesive according to claim
 3. 14. A coating material comprising the adhesive bond according to claim
 4. 15. A furniture product comprising the adhesive bond according to claim
 4. 16. An automobile or automobile component comprising the adhesive bond according to claim
 4. 17. A shoe or shoe component comprising the adhesive bond according to claim
 4. 18. A textile or textile component comprising the adhesive bond according to claim
 4. 19. A window or window component comprising the adhesive bond according to claim
 4. 20. The reactive hotmelt adhesive according to claim 3, wherein hexanediol, nonanediol, decanediol and dodecanediol are used as diols of the formula HO—(CH₂)_(x)—OH. 